Base for plastic container

Abstract

A molded polymeric container includes a body portion having a sidewall and an integral champagne type base. The base includes a lower end that defines an annular contact ring for supporting the container with respect to an underlying surface. An annular step ring is defined immediately radially inwardly of the annular contact ring and has a radial length LS. The base further has a central push-up area and a generally concave transition region interposed between the central push-up area and the annular contact ring. The transition region further includes a plurality of integrally molded radially extending ribs, each of the ribs having a length LR. According to one advantageous aspect of the invention, the ratio LR/LS is within a range of about 1.0 to about 4.0.

What is claimed is:  
     
       1. A molded polymeric container, comprising: 
       a body portion having a sidewall; and  
       a champagne type base portion that is molded integrally with said sidewall, said champagne type base portion comprising  
       a lower end that defines an annular contact ring for supporting the container with respect to an underlying surface;  
       an annular step ring defined immediately radially inwardly of said annular contact ring, said annular step ring including at least one top step and at least one bottom step, said annular step ring further having an inner radius, an outer radius and a radial length L s representing a distance between said inner and outer radii;  
       a central push-up area;  
       a generally concave transition region interposed between said central push-up area and said annular contact ring, said transition region further comprising a plurality of integrally molded radially extending ribs that are located radially inwardly of said inner radius of said annular step ring, each of said ribs having a length L R ; and wherein  
       the ratio of said length L R  of said radially extending ribs divided by said radial length L S  is within a range of-about 1.0 to about 4.0.  
     
     
       2. A molded polymeric container according to  claim 1 , wherein the ratio of said length L R  of said radially extending ribs divided by said radial length L S  is within a range of about 2.5 to about 3.0. 
     
     
       3. A molded polymeric container according to  claim 2 , wherein the ratio of said length L R  of said radially extending ribs divided by said radial length L S  is about 2.7. 
     
     
       4. A molded polymeric container according to  claim 1 , wherein each of said radially extending ribs has a maximum depth D R , and wherein said maximum depth D R  is within a range of about 0.05 to about 0.25 of the length L R  of said radially extending ribs. 
     
     
       5. A molded polymeric container according to  claim 4 , wherein each of said radially extending ribs has a maximum depth D R , and wherein said maximum depth D R  is within a range of about 0.1 to about 0.18 of the length L R  of said radially extending ribs. 
     
     
       6. A molded polymeric container according to  claim 5 , wherein each of said radially extending ribs has a maximum depth D R , and wherein said maximum depth D R  is about 0.13 of the length L R  of said radially extending ribs. 
     
     
       7. A molded polymeric container according to  claim 1 , wherein said annular step ring has a depth D S , and wherein said depth D S  is within a range of about 0.2 to about 0.5 of the radial length L S  of the annular step ring. 
     
     
       8. A molded polymeric container according to  claim 7 , wherein said annular step ring has a depth D S , and wherein said depth D S  is within a range of about 0.3 to about 0.5 of the radial length L S  of the annular step ring. 
     
     
       9. A molded polymeric container according to  claim 8 , wherein said annular step ring has a depth D S , and wherein said depth D S  is about 0.39 of the radial length L S  of the annular step ring. 
     
     
       10. A molded polymeric container according to  claim 1 , wherein said generally concave transition region has a radius of curvature R RB , and wherein each of said radially extending ribs has a convex outer radius of curvature R RT , and wherein the ratio R RT /R RB  is within a range of about 0.6 to about 1.0. 
     
     
       11. A molded polymeric container according to  claim 10 , wherein said generally concave transition region has a radius of curvature R RB , and wherein each of said radially extending ribs has a convex outer radius of curvature R RT , and wherein the ratio R RT /R RB  is within a range of about 0.75 to about 0.9. 
     
     
       12. A molded polymeric container according to  claim 11 , wherein said generally concave transition region has a radius of curvature R RB , and wherein each of said radially extending ribs has a convex outer radius of curvature R RT , and wherein the ratio R RT /R RB  is about 0.82. 
     
     
       13. A molded polymeric container according to  claim 1 , wherein said annular step ring defines a concave circumferentially extending top step that has a radius of curvature R ST , and a plurality of radially extending bottom steps, each of which has a convex radius of curvature R SB . 
     
     
       14. A molded polymeric container according to  claim 13 , wherein said annular step ring is constructed and arranged so that a ratio R SB /R ST  is within a range of about 0.5 to about 1.0. 
     
     
       15. A molded polymeric container according to  claim 14 , wherein said annular step ring is constructed and arranged so that a ratio R SB /R ST  is within a range of about 0.65 to about 0.85. 
     
     
       16. A molded polymeric container according to  claim 15 , wherein said annular step ring is constructed and arranged so that a ratio R SB /R ST  is about 0.75. 
     
     
       17. A molded polymeric container according to  claim 1 , wherein said central push-up area has a radius R O , and wherein said base portion has an outer radius R B , and wherein the ratio R RB  is within a range of about 0.15 to about 0.25. 
     
     
       18. A molded polymeric container according to  claim 17 , wherein the ratio R O /R B  is about 0.15 to about 0.25. 
     
     
       19. A molded polymeric container according to  claim 18 , wherein the ratio R O /R B  is about 0.19. 
     
     
       20. A molded polymeric container according to  claim 1 , wherein relative dimensions of said base portion are selected substantially according to the formula:        Hp   =       [     Hb   +     2        (     Rb   -   Rc     ]     *     (       P   TcRc     -   1     )     *     (     Rc   -   Ro     )             2        (     Rb   -   Rc     )                         
       wherein: 
       H p  is the height of the central push-up area;  
       P is a preform index that is equal to the thickness T p  of the preform times the middle radius R, of the preform;  
       H b  is the height of the base portion;  
       R b  is the maximum outer radius of the base portion;  
       R c  is the radius of the annular contact ring;  
       T c  is the thickness of molded plastic material in the area of the annular contact ring; and  
       R o  is the radius of the central push-up area.  
     
     
       21. A molded polymeric container according to  claim 20 , wherein a ratio R c /R b  is within a range of about 0.65 to about 0.74. 
     
     
       22. A molded polymeric container according to  claim 21 , wherein T c  is within a range of about 0.06 to about 0.09 inches. 
     
     
       23. A molded polymeric container, comprising: 
       a body portion having a sidewall; and  
       a champagne type base portion that is molded integrally with said sidewall, said champagne type base portion comprising  
       a lower end that defines an annular contact ring for supporting the container with respect  
       to an underlying surface;  
       an annular step ring defined immediately radially inwardly of said annular contact ring, said annular step ring having a radial length L S  and a depth D S , and wherein said depth D S  is within a range of about 0.2 to about 0.5 of the radial length L S  of the annular step ring;  
       a central push-up area;  
       a generally concave transition region interposed between said central push-up area and said annular contact ring, said transition region further comprising a plurality of integrally molded radially extending ribs, each of said ribs having a length L R ; and wherein  
       the ratio of said length L R  of said radially extending ribs divided by said radial length L S  is within a range of about 1.0 to about 4.0.  
     
     
       24. A molded polymeric container according to  claim 23 , wherein said annular step ring has a depth D S , and wherein said depth D S  is within a range of about 0.3 to about 0.45 of the radial length L S  of the annular step ring. 
     
     
       25. A molded polymeric container according to  claim 24 , wherein said annular step ring has a depth D S , and wherein said depth D S  is about 0.39 of the radial length L S  of the annular step ring. 
     
     
       26. A molded polymeric container, comprising: 
       a body portion having a sidewall; and  
       a champagne type base portion that is molded integrally with said sidewall, said champagne type base portion comprising  
       a lower end that defines an annular contact ring for supporting the container with respect to an underlying surface;  
       an annular step ring defined immediately radially inwardly of said annular contact ring, said annular step ring having a radial length L S ;  
       a central push-up area;  
       a generally concave transition region interposed between said central push-up area and said annular contact ring, said transition region further comprising a plurality of integrally molded radially extending ribs, each of said ribs having a length L R , said generally concave transition region having a radius of curvature R RB , and wherein each of said radially extending ribs has a convex outer radius of curvature R RT , and wherein the ratio R RT /R RB  is within a range of about 0.6 to about 1.0; and wherein  
       the ratio of said length L R  of said radially extending ribs divided by said radial length L S  is within a range of about 1.0 to about 4.0.  
     
     
       27. A molded polymeric container according to  claim 26 , wherein said generally concave transition region has a radius of curvature R RB  and wherein each of said radially extending ribs has a convex outer radius of curvature R RT , and wherein the ratio R RT /R RB  is within a range of about 0.75 to about 0.9. 
     
     
       28. A molded polymeric container according to  claim 27 , wherein said generally concave transition region has a radius of curvature R RB , and wherein each of said radially extending ribs has a convex outer radius of curvature R RT , and wherein the ratio R RT /R RB  is about 0.82. 
     
     
       29. A molded polymeric container, comprising: 
       a body portion having a sidewall; and  
       a champagne type base portion that is molded integrally with said sidewall, said champagne type base portion comprising  
       a lower end that defines an annular contact ring for supporting the container with respect to an underlying surface;  
       an annular step ring defined immediately radially inwardly of said annular contact ring, said annular step ring having a radial length L S ,said annular step ring defining a concave circumferentially extending top step that has a radius of curvature R ST , and a plurality of radially extending bottom steps, each of which has a convex radius of curvature R SB .  
       a central push-up area;  
       a generally concave transition region interposed between said central push-up area and said annular contact ring, said transition region further comprising a plurality of integrally molded radially extending ribs, each of said ribs having a length L R ; and  
       wherein the ratio of said length L R  of said radially extending ribs divided by said radial length L S  is within a range of about 1.0 to about 4.0.  
     
     
       30. A molded polymeric container according to  claim 29 , wherein said annular step ring is constructed and arranged so that a ratio R RT /R ST  is within a range of about 0.5 to about 1.0. 
     
     
       31. A molded polymeric container according to  claim 30 , wherein said annular step ring is constructed and arranged so that a ratio R RT /R ST  is within a range of about 0.65 to about 0.85. 
     
     
       32. A molded polymeric container according to  claim 31 , wherein said annular step ring is constructed and arranged so that a ratio R RT /R ST  is about 0.75. 
     
     
       33. A molded polymeric container, comprising: 
       a body portion having a sidewall; and  
       a champagne type base portion that is molded integrally with said sidewall, said champagne type base portion comprising  
       a lower end that defines an annular contact ring for supporting the container with respect to an underlying surface;  
       an annular step ring defined immediately radially inwardly of said annular contact ring, said annular step ring having a radial length L S ;  
       a central push-up area;  
       a generally concave transition region interposed between said central push-up area and said annular contact ring, said transition region further comprising a plurality of integrally molded radially extending ribs, each of said ribs having a length L R ; and wherein said base portion is shaped so that for any given radial cross-section one of said annular step ring and said transition region has a concave profile while the other of said annular step ring and transition region has a convex profile.